Mel Gibson and Oksana Grigorieva, his Russian musician-singer girlfriend and mother of their 5-month-old daughter, have split after over a year of dating, a source tells PEOPLE.
"They just drifted apart," says a close friend of the couple of the amicable split. "They’re both working hard on their careers and trying to raise a sweet baby together. They're still friends and they'll both raise Lucia together."
Gibson is in Mexico filming How I Spent My Summer Vacation, and Grigorieva is working on her music. Next week, she has plans to perform a charity concert in Russia to benefit "Grant Life," a foundation to help children with cancer and other life-threatening illnesses